1.FIELD OF THE INVENTION
The present invention relates to a multiple electrical sensor positioning device. More particularly, it relates to a universal sensor mask and its method of use with diagnostic medical equipment. More particularly still, the present invention relates to a disposable dermal chest mask for assistance in establishing physical attachment of sensors from electrocardiograph machines to a human chest.
2. DESCRIPTION OF THE PRIOR ART
Prior art electrodes for contacting a specific area of the human body for use with diagnostic medical equipment are generally a combination of elements. A signal wire from the analytical apparatus is usually attached to a metallic or otherwise conductive body contact electrode which is attached to the patient's skin at the desired point of contact. The wire and electrode combination are generally referred to as a "lead." Electrical current generated by the heart in a person's chest flows to the surface and at the skin produces differences in electrical voltage which can be measured between pairs of electrodes placed at two points on the skin. One of the most common tests performed requiring electrode attachment to a patient's body is an electrocardiogram, sometimes alternatively referred to as an ECG. A twelve-lead electrocardiograph provides the most accurate signals for recognizing ischemic electrocardiographic changes.
To administer a resting twelve-lead ECG, it is necessary to apply ten electrodes to various points on the torso and limbs of a patient to measure and analyze cardiac data. Twelve recordings for the ECG are made from nine active lead positions with the tenth being used as a ground. An electrode portion of a lead may in fact consist of an alternative form of sensor, and the terms "electrode" or "sensor" for purposes of this disclosure are interchangeable. A lead wire connecting a sensor to the diagnostic equipment could possibly in fact consist of a radio or an optical signal. Six of the ten electrodes are applied to the patient's chest over prescribed anatomical landmarks. The remaining four electrodes are applied to each of the patient's limbs. The chest electrodes are known as the precordial leads and the limb electrodes are called limb leads. The precordial leads are designated V.sub.1, V.sub.2, V.sub.3, V.sub.4, V.sub.5, and V.sub.6. The limb leads are designated LA, RA, LL, and RL (ground).
It is generally acknowledged that it is critically important to place the precordial leads with precision in order to obtain accurate and repeatable recordings. However, accurate placement and attachment of a large number of leads can be difficult and time consuming and requires knowledge, skill, and diligence on the part of the person attaching the electrodes or sensors. Mechanical problems in attaching multiple leads to a patient range from tangling of lead wires and excessive time consumed in pairing lead wires with the appropriate electrodes, to difficulty in locating anatomical landmarks on a patient with precision.
Problems occur if the leads are not properly placed and are located higher or lower than optimal. The position of the precordial leads is determined by the anatomical features of the patient's chest and not by the position of the heart itself. Research reported in the electrocardiography literature indicates that precordial leads placed one inch or more from their true anatomical landmarks can result in misinterpretation of the patient's ECG. This may result in or contribute to diagnosis errors, false hospital admissions, sending sick people home, or have other negative impacts on diagnosis or treatment. The placement problem is compounded when serial comparisons are made between two or more ECGs taken over time. For example, if V.sub.4 was placed one inch too high for one test and one inch too low for another, the difference of two inches may produce what appears to be a significant difference between the two ECGs when in fact there was no physiological change in the patient's heart condition.
To place the precordial leads accurately requires training in using both visual and palpatory cues to find the anatomical landmarks on each patient. Placement accuracy is also affected by the time and diligence dedicated to placing the precordial electrodes. An experienced and conscientious electrocardiologist may require and devote ten minutes to palpation and ascertaining the exact precordial landmarks. However, in busy clinical environments or emergency situations, medical personnel are often so rushed they may not even palpate the patient. Under those conditions, precordial leads are commonly placed with inadequate palpation and with little attention to a patient's particular anatomy. As a consequence, individual leads are often misplaced by two and as much as three inches from their true anatomical landmarks. In addition, training and maintaining the necessary skill for proper placement of individual leads is time and resource consuming and often not adequate. With six precordial leads, there are six chances to misplace electrodes. Research shows that V.sub.1, and V.sub.2 electrodes are typically placed high and wide of their targets--the fourth intercostal space on each side of the sternum. Likewise, precordial electrodes V.sub.4, V.sub.5, and V.sub.6 are most often misplaced low and wide. Electrode V.sub.3 is most often misplaced too low. The most obvious conclusion to be drawn is that lead placement is often not accurate.
After the individual electrodes are positioned on a patient, it is necessary to attach the ten lead wires. Each lead wire is labeled to correspond to one of the anatomical landmarks, i.e., V.sub.1, V.sub.2 . . . V.sub.6 . . . RL. Should lead wires be crossed, interpretative ECG monitors can detect and alert the operator of a possible crossed lead wire situation, but that requires additional time to check connections and to take corrective action. This is a time consuming operation which increases the risk in an emergency situation. Crossed lead wires are a more significant problem when the ECG monitor does not provide interpretation of the recordings and cannot alert the operator of this possibility. In such a case, the ECG signals for each of the twelve leads are recorded on hard copy to be read at a later time. The physician or technician reading the ECG recordings may recognize the error but by that time the patient has usually been disconnected from the monitor. The present invention reduces or eliminates the chances of either of these situations from occurring.
Periodic electrocardiograms are important for providing a cardiographic profile of a patient for early detection and diagnosis of cardiovascular diseases. In order to provide an accurate profile, it is important not only that the electrocardiogram be taken with sensors affixed accurately, but that the sensors be placed at the same location on the patient in the subsequent exam as for the previous examination. The efficacy and the repeatability of the tests is critical so that a series of ECG results can be compared to provide a continuing profile of a patient's medical history for diagnosis and treatment of heart disease.
In urgent situations, including those electrocardiograms taken with the current standard electrode lead wire system, during an acute symptomatic episode there may only be time to attach two to four individual electrodes to the patient There, it is desirable to have a device which enables more electrodes or sensors to be quickly and accurately secured during such an acute symptomatic episode. Alternatively, it may be necessary to quickly remove some or all of the chest leads when a patient is experiencing a heart attack or in other emergencies in order to administer CPR, to massage the heart, administer drugs, to apply electrical defibrillation paddles, or for other purposes. Accordingly, critical time can be lost both in the removal of the chest leads of the ECG test equipment in order to administer aid to a patient and in their subsequent replacement after aid has been administered.
Because of the inadequacies of prior art devices to solve these problems, there has been a need for a system which: prevents or curtails the possibility of ECG electrode leads or wires from being entangled or crossed; provides quick removal of some of the sensors when it is necessary to administer aid to a patient having a heart attack; provides accurate and appropriate repeatable placement of electrodes it substantially the same location on the patient; accurately and repeatedly obtains signals from electrodes by efficient and effective electrical transmission; and may be attached by persons with varying levels of experience including those with little training.
The inventions disclosed in the above-identified four related applications involve various alternatives for the purpose of trying to effect those goals. The common invention in those applications is a disposable electrode positioning device and utilizes a non-conducting flexible sheet having a predetermined dimensional sensor array. The flexible sheet serves as a template for aligning connectors or sensors, either of the electrode or electrodeless type, on the chest of a patient for transmitting electrical impulses. The sheet has a predetermined dimensional sensor array V.sub.1 -V.sub.6, such that V.sub.1 and V.sub.2 are positioned approximately on either side of the sternum at the fourth intercostal space, and array V.sub.3 is positioned midway between V.sub.2 and V.sub.4. V.sub.5 is equidistant between V.sub.4 and V.sub.6. The distance between V.sub.1 and V.sub.2 is predetermined plus or minus a small amount and they are both equidistant from the centerline of the sternum. The distance between V.sub.2 and V.sub.4 is predetermined plus or minus a small amount, and V.sub.3 is located substantially midway between V.sub.2 and V.sub.4.
An important aspect of the related inventions is that the flexible non-conductive sheet is provided in a plurality of sizes, with each size having arrays V.sub.1, V.sub.2, V.sub.3 and V.sub.4, at substantially the same locations and having arrays V.sub.5 and V.sub.6 at different locations depending on size. In this regard, the locations of V.sub.5 and V.sub.6 are based on a measured distance between the left midlavicular line and the left midaxillary line on the chest of a patient.
An alternative of the related inventions is that the dimensional array on the flexible nonconductive sheet is provided with cutouts to form a template or mask which is placed on the patient's chest and then conventional electrodes can be positioned in the cutouts. Still another aspect of the related inventions is that the template can be provided with a plurality of conventional tab, snap, or other electrodes affixed on their top sides to the flexible sheet to be placed against the patient's chest. The electrodes are positioned in accordance with the predetermined dimensional array. Small cutouts, or openings, in the template expose the electrode tabs for attaching lead wire clips. Snap electrodes protrude through the template to permit the attachment of lead wire snap connectors.
In a further aspect of the related inventions, the top sides of individual electrodes can be lightly affixed to the flexible sheet of material at the predetermined dimensional array locations. The sheet can be placed on the patient's chest and then peeled away leaving the electrodes properly located on the chest. Each of these concepts can be employed in the new and improved concept of the present invention.
Yet another aspect of those related inventions is a method of sizing a patient for fitting a sensor positioning device having a flexible sheet with a fixed dimensional V.sub.1 -V.sub.6 array positioned in a specific size configuration appropriate for standard electrocardiographic recording. The distance between V.sub.2 and V.sub.1 is a predetermined distance plus or minus a small amount, and the distance between V.sub.2 and V.sub.4 is a predetermined distance plus or minus a small amount, with V.sub.3 located substantially midway between V.sub.2 and V.sub.4, and V.sub.5 being equidistant between V.sub.4 and V.sub.6. The method of sizing the disclosed related inventions comprises the steps of measuring the distance between the midlavicular line and a midaxillary line on the chest of the patient, and selecting a positioning device size of those inventions based on the measured distance. This procedure is eliminated by the present invention.
The prior art U.S. Pat. No. 4,583,349 to Manoli and U.S. Pat. No. 5,507,290 to Kelly describe precordial electrodes fixed in a preset pattern on a flexible sheet in positions corresponding to the anatomical landmarks on the patient. The basic problem with all of these inventions is that they require multiple sizes of sensor positioning devices to fit various sized persons.
Manoli envisions, without stating any dimensions, three sizes--a pediatric, medium adult, and large adult--to fit most children and adults within the population. Kelly describes three sizes--small, medium, and large adult--to fit most adults within the population. Manoli does not describe how one determines which size device a patient would require. Presumably, under Manoli, a small person requires the smallest of the three sizes, i.e., the pediatric, and a large person requires the largest. The invention disclosure is indefinite.
Thus, Manoli does not describe how to size a patient, and it is common for persons placing individual electrodes to make errors. If similar errors are made when sizing the patient for Manoli's device, it is quite likely that the wrong size device would be selected. Once a device is applied to the patient, it would be possible to check the correctness of fit. If wrong, however, i.e., the V.sub.6 electrode was located some distance from the patient's midaxillary line, the device would have to be removed and replaced by a more appropriate size device. This trial and error approach wastes time and materials since the first device would need to be discarded without ever being used to take an ECG.
The more recent U.S. Pat. No. 5,678,545 to Stratbucker describes an adhesive sheet having a fixed array of individual electrode groups disposed at varying locations to provide a "one size fits all" system. One embodiment has twelve precordial electrodes with one electrode each at V.sub.1, V.sub.2, and V.sub.3 and groups of three electrodes each at V.sub.4, V.sub.5, and V.sub.6, while other embodiments are suggested for groups of electrodes for other electrode locations in order to achieve a "one size fits all" system.
Stratbucker describes multiple groupings of electrodes for a "single size" system but it is necessary to determine which electrode in each group is within the region of the appropriate location on a patient's chest: for each group of electrodes, there must be a determination of which electrode is closest to the anatomical landmark. Such a determination is time consuming and would at least be impeded by the fact that palpation will be difficult to perform once the sheet is placed over a patient's chest. Moreover, each group of electrodes provides a source for error since there are three electrodes to choose from in each group. Assuming one electrode in each group is most correct, the probability of randomly selecting the best electrode from each of the groups is 0.33.sup.x, where X equals the number of groups. If there are three groups of electrodes, as described in one embodiment where V.sub.4, V.sub.5, and V.sub.6 consist of groups of three electrodes each, the probability of randomly selecting the appropriate electrode from each group is 0.037, or 1 out of 27 possibilities. Stratbucker relies on a judgment determination for each group of electrodes and therefore selection is time consuming and inexact due to the device physically covering the patient's anatomical features.
Although Stratbucker tries to curtail the possibility of placing conventional individual electrodes far from the region of proper placement by confining the decision to simply selecting one electrode out of each group of three electrodes, medical personnel must still ascertain which electrode is appropriate for each group of electrodes. Not only does this allow for error, it also reduces the chances of consistent electrode placement from one test to the next, thereby confounding any serial comparisons between tests. It also increases the length of time to administer a resting ECG since a separate decision must be made for each group of electrodes.
The present invention uniquely solves these problems by providing a multiple precordial array of sensor electrodes in a single device that will fit essentially all adults and in which sizing is accomplished simply by the determination of the location of a single sensor which is closest to a selected anatomical landmark. This is achieved by the invention of a device having more precordial sensors than the six chest electrodes needed for the resting ECG but significantly less than the number of those taught by Stratbucker. In the present invention, some sensors may serve multiple roles to accommodate different patient sizes within one array by utilizing a particular set of sensors. Each set of sensors corresponds to a specific patient size that can be characterized as small, medium, or large. Once the device of the invention is applied to the patient, one simply and quickly ascertains which of three V.sub.6 sensors lies on or closest to the patient's midaxillary line and then connects the electrode/sensor lead wires to the corresponding set of sensors in which the V.sub.6 is designated as one of the three selections: small, medium, or large. This greatly simplifies the heretofore universal unresolved problem of instantaneous patient sizing during use, while providing the additional benefits of reducing the cost of production and eliminating the need to stock different size devices.
Another aspect of the present invention is a mask comprised of conductive terminals that are selectively connected to an ECG machine by a single point of attachment or an electronic clip. The clip mechanism includes a means of accurately connecting to any set of terminals by means of a positioning feature on the clip that selectively brings each set of terminals into precise alignment with conducting elements within the clip. Essentially, the selective connection system makes electrical contact with only one set of precordial sensors at a time, i.e., one particular set containing V.sub.1 through V.sub.6, and excludes the remainder.
Sensors V.sub.1 and V.sub.2 on the device are centered over the patient's sternum in the left and right fourth intercostal spaces. Once V.sub.1 and V.sub.2 are applied, all remaining sensors are automatically applied by bringing the flexible sheet down on the patient. The particular V.sub.6 sensor closest to the patient's midaxillary line automatically identifies which set of sensors are to be connected to an ECG machine. The clip is then used to selectively connect that set of precordial sensors to the ECG machine.